With the rapid and continuous development of science and technology, ever increasing numbers of new technologies as well as associated products in various fields have been successfully presented in commercial markets, largely enhancing/facilitating human daily life and improving living quality. In the area of communications, the mobile or cellular telephone provides one example of such technology. Before its invention, people had to remain close to stationary telephones to avoid missing important calls. With the invention of cell phones, such a problem was easily solved. Users can stay in contact at any time no matter where they are or what they are doing, typically without inducing much interference in daily activities.
More recently, with the increasing standard of human living and increasing technological capabilities, cell phones that provide only simple audio functions no longer meet market demands or requirements. Additional functional devices or modules have been gradually developed and have subsequently evolved, making cell phones more and more versatile and intelligent. A miniature camera is one such module, by way of which video communication and image/video capture functions can be implemented. Due to their excellent portability and powerful functionality, present-day smart phones are very popular and have become one of the most indispensable devices in daily life. Today, nearly two billion mobile phones have digital cameras, and an additional 800 million smart phone cameras are shipped each year. Besides the aforementioned smart phones, miniaturized cameras also find wide-spread applications in various civilian and military fields, including endoscopes for healthcare, security cameras, and surveillance cameras for unmanned aerial vehicles (UAVs) and micro aerial vehicles (MAVs). Given this extremely large market perspective, miniature cameras have garnered much interest from researchers from academia to industries, all over the world.
Many efforts have been taken to improve the performances of miniaturized digital cameras so as to make their operation closer to that of traditional digital cameras. In the early stages of miniature digital camera development, the associated optical system was intentionally designed to possess a long depth of focus. Such an optical system could simultaneously provide clear images of nearly all objects in the field of view without requiring an auto-focusing function. This treatment largely simplified system configuration, but such simplification occurred at the expense of lower image contrast as well as reduced or suboptimal image quality. Although better image and video quality has been realized though increasing pixel numbers and improving corresponding hardware and software associated with image processing, more sophisticated functions such as autofocus and zoom are still in great demand and await technological breakthroughs.
Unlike their traditional counterparts, miniaturized digital cameras must meet dimensional requirements associated with limited or very limited available space. Hence, conventional autofocus and zoom mechanisms are not appropriate for miniaturized digital cameras due to the bulky volume of such mechanisms. Implementation of these functionalities in miniature digital cameras thus poses a challenging technical problem.